1. Field of the Invention
The present disclosure refers to an electrode lead in particular for use with a medical implant.
2. Description of the Related Art
Electrode leads for such use are known in a wide variety of embodiments, e. g. cardiac pacemaker leads for sensing and/or pacing, or active leads for implantable defibrillators. A problem occurs with such electrode leads, when they are placed in strong dynamic magnetic fields, like is the case during magnetic resonance imaging or close to radio transmission stations. Due to electromagnetic interference (EMI), radio frequency (RF) energy is picked up by the electrode lead. This energy exits the electrode lead at an electrode pole, which is connected and/or connectable to the electrode lead, like a tip electrode of a pacemaker electrode lead. Due to the high frequency, the exiting energy causes a heating of the surrounding tissue or blood what in turn may destroy the surroundings of the electrode, such as living tissue. Within the cardiac environment, this can increase e.g., pacing thresholds of an electrode lead used as a pacemaker lead, in the worst case this heating may make the lead ineffective.
The aforesaid problems are broadly discussed in U.S. Pat. No. 7,363,090 B2 which discloses a basic solution concept for the problem of the energy induced in an electrode lead by RF energy during MRI, namely, integrating a band stop filter into each lead wire leading to a ring and/or tip electrode of an electrode lead of an active implantable medical device (AIMD). This band stop filter includes a capacitor in parallel with an inductor. The parallel capacitor and inductor are placed in series with the implantable lead wire of the AIMD, wherein values of capacitance and inductance are selected such that the band stop filter is resonant at a selected frequency. In a preferred embodiment of the known electrode lead with band stop filter, the latter is integrated into the tip and/or ring electrode for the active implantable medical device.
Such electrode leads used in practice, as they are produced and marketed by the applicant of U.S. Pat. No. 7,363,090 show filter constructions in which the capacitor and the inductor are hermetically sealed in a drum which forms a cylindrical stiff element of considerable dimensions. Due to the large and bulky housing of this known filter, the electrode lead equipped with this filter has an unacceptable stiff tip section which is problematic when introducing the electrode lead into a body vessel. Bulky long stiff regions in the tip section may cause perforation of the body vessel which is a serious incident when positioning the electrode lead.
A further disadvantage of the known electrode lead with band stop filter is the fact that the electrode lead does not dispose of a central continuous lumen for guiding the electrode lead over a guide wire or mandrel because of the bulky massive filter element.